The subject matter of the present invention relates generally to tube adjustment gaskets which resiliently lock a threadedly connected tube against accidental rotation without damaging the tube, while permitting manual rotational adjustment of such tube. More particularly, the present invention relates to adjustment gaskets of synthetic plastic material which have concave arcuate surface portions separated by flat surface portions to enable longitudinally compression of the gasket. The compressed gasket between a pair of threadedly connected tubes maintains the tubes in resilient tension to lock them against accidental rotation, while enabling rotational adjustment of such tubes over the compression range of the gasket. The adjustment gasket of the present invention can be used in a rifle scope between threadedly interconnected tubular members, such as between the eyepiece lens tube and the turret housing or between the objective lens tube and the turret housing of such scope to rotationally align the eyepiece lens and the objective lens with the turret housing. This is especially useful during the manufacturing of such rifle scope in that it enables a pair of interconnected tubes to be adjusted to their proper calibrated rotational position and maintained in such adjusted position during further manufacturing steps until they are permanently fixed into position by glue. Thus, the adjustment gasket avoids the need for matched parts machining to provide matched pairs of tubes which must be maintained together as a matched pair during manufacturing. This considerably reduces the expense of manufacture.
It has previously been proposed in U.S. Pat. No. 3,390,713 of Gutshall, issued July 2, 1968 to provide a metal lock washer of undulated shape with flat locking abutments projecting from the bottom of the undulation valleys. However, this lock washer is not made of synthetic plastic material and the metal locking projections have a "chisel-like edge" which embeds into and damages the workpiece or bolt nut between which it is clamped. Also, the lock washer is not provided with flat portions between concave arcuate portions on each side of such washer to enable longitudinal compression without damaging the workpiece in the manner of the present invention.
Metal lock washers such as that of U.S. Pat. No. 299,977 of Garvey granted June 10, 1884, as well as, British Pat. No. 108,937 of Webb granted Aug. 30, 1917 and Italian Pat. No. 372,823 of Thode granted in 1939 are unsuitable as adjustment gaskets for threadedly connected tubes because the sharp metal projections of such lock washers damage the workpiece. Thus, like the above discussed Gutshall patent, their metal projections dig into and embed into the workpieces to lock them against rotation and can only be adjusted when considerable force is exerted by means of a wrench or other similar tool. However, with the plastic adjustment gasket of the present invention, the interconnected tubes can have their rotational position adjusted manually while the gasket maintains such tubes under resilient tension over the compression range of the gasket.
U.S. Pat. No. 4,191,872 of Sorenson granted Mar. 4, 1980 and U.S. Pat. No. 4,257,465 of Berg granted Mar. 24, 1981, both show lock washers made of synthetic plastic material. However, they operate in an entirely different manner and they are not provided with an undulated shape to enable longitudinal compression of the washer. The lock washer of Sorenson is flat with two key type locking projections which are inserted into key openings in the workpieces so there is no longitudinal compression of the washer. Also, the lock washer of Berg provides conical locking projections which are bent to provide locking without longitudinal compression of the washer body. Thus, neither of these patents show a lock washer of undulated shape having alternate concave arcuate areas and flat areas on each side thereof to enable longitudinal compression of the washer and resilient locking without damage to the workpiece, in the manner of the adjustment gasket of the present invention.
In addition, it has been previously proposed in U.S. Pat. No. 579,643 of Gleason, granted Mar. 30, 1897 to provide a pipe coupling made of the metal lead which is not resilient, but is provided with indentations or teeth on the opposite side thereof. These teeth mate with the teeth of two pipe coupling collars threadedly attached to the outside of the pipes, compressing such coupling to prevent relative movement and leakage between the pipes. Thus, this pipe coupling is for an entirely different purpose than the resilient plastic adjustment gasket of the present invention.
The adjustment gasket of the present invention and tube assemblies employing such gasket have the advantage of providing manual rotational adjustment of the interconnected tubes while maintaining the tubes in resilient locked condition to prevent accidential rotation thereof, in a simple and inexpensive manner. The adjustment gaskets do not damage the tubes or other workpieces and are reuseable since they are made of resilient synthetic plastic material. Furthermore, the adjustment gasket of the present invention is capable of sufficient longitudinal compression to enable a full 360.degree. rotational adjustment of the interconnected tubular members while maintaining them in resilient tension over the compression range of the gasket. By providing the gasket with an undulating shape including a plurality of concave arcuate surface areas alternating with flat surface areas on one or both sides of the gasket, such gasket is provided with a large longitudinal compression range greater than one-half the minimum longitudinal thickness of the gasket as measured between the flat area on one side and the bottom of the arcuate portion on the opposite side of such gasket. A rifle scope employing the adjustment gasket between threadedly connected tubes thereof is easier and less expensive to manufacture since it does not require custom matched machining of parts or matched pairs of tubes.